I have one HomeActivity from where I am calling the list of fragments. In HomeActivity I have sidemenu where all fragments are loaded.
Now,in this list i have one fragment called HomeFragment which display the Google Map with data, using webservice.
What i want is i want to load the Map dat only once(first time) fragment is loaded, not every time when click on sidemenu or come in from any other fragment.
My HomeFragment or any other fragments are loaded at once, not every time.
You can hide/show fragment. No need to replace, remove. For ex, I have 2 fragments FragmentFeed and FragmentNotification, we can hide/show or add fragment.
Handle click menu:
if (tabId.equals(AppConstants.FEED)) {
pushFragments(tabId, getFragmentFeed());
} else if (tabId.equals(AppConstants.NOTIFICATION)) {
pushFragments(tabId, getFragmentNotification());
}
Handle show/hide and add fragment:
public void pushFragments(String tag, Fragment fragment) {
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction ft = manager.beginTransaction();
if (manager.findFragmentByTag(tag) == null) {
ft.add(R.id.realtabcontent, fragment, tag);
}
Fragment fragmentFeed = manager.findFragmentByTag(TAG_FEED);
Fragment fragmentNoti = manager.findFragmentByTag(TAG_NOTIFICATION);
// Hide all Fragment
if (fragmentFeed != null) {
ft.hide(fragmentFeed);
}
if (fragmentNoti != null) {
ft.hide(fragmentNoti);
}
// Show current Fragment
if (tag == TAG_FEED) {
if (fragmentFeed != null) {
ft.show(fragmentFeed);
}
}
if (tag == TAG_NOTIFICATION) {
if (fragmentNoti != null) {
ft.show(fragmentNoti);
}
}
ft.commitAllowingStateLoss();
}
You should use two things.
First onSavedInstance of your Fragment.
Fill it with the info you want.
Second setRetainState(true). This will prevent your fragment from destroying even if it is detached. Hope this helps.
In my activity I have 2 fragments of a same type but different instances and I want to show one and hide the other when different button is pressed.
Here is the code for adding fragments to the activity:
_pardisCinemaFragment = NewsListingFragment.newInstance(TAB_CINEMA);
_shoppingFragment = NewsListingFragment.newInstance(TAB_SHOPPING);
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.setCustomAnimations(
R.anim.enter_from_left,
R.anim.exit_to_left,
R.anim.enter_from_left,
R.anim.exit_to_left);
transaction.addToBackStack(null);
transaction.add(R.id.news_list_fragment_container, _pardisCinemaFragment);
transaction.add(R.id.news_list_fragment_container, _shoppingFragment);
transaction.commit();
and here's the onclick event:
public void onTabClick(View view) {
String tag = view.getTag().toString();
Fragment fragmentToShow = null;
Fragment fragmentToHide = null;
if(tag.equals(TAB_CINEMA) && !currentTab.equals(TAB_CINEMA)) {
currentTab = TAB_CINEMA;
fragmentToShow = _pardisCinemaFragment;
fragmentToHide = _shoppingFragment;
}
else if(tag.equals(TAB_SHOPPING) && !currentTab.equals(TAB_SHOPPING)) {
currentTab = TAB_SHOPPING;
fragmentToShow = _shoppingFragment;
fragmentToHide = _pardisCinemaFragment;
}
if(fragmentToHide != null && fragmentToShow != null) {
getFragmentManager().beginTransaction()
.setCustomAnimations(android.R.animator.fade_in, android.R.animator.fade_out)
.hide(fragmentToHide)
.show(fragmentToShow)
.commit();
}
}
but nothing happens and it doesn't hide then show the fragments. is it because of the way they are added?
I understand that if one of the fragments are supposed to be hidden at first, there is no need to add it until the user presses the button but since some data has to be populated into the fragment view from phone's database I want it to be happening at the back while it's not visible.
I have a problem with android fragment backstack. This is my situation.
// I can't post images yet, so I passed a link to it.
As you can see, I want to go from Fragment 1 to Fragment 2 and at the end to Fragment 3, but when I press back button at Fragment 3, I want to back to Fragment 1.
I do this like I describe on pic, but when I press Back Button nothing happen and when I press it second time, the app is closing.
My BackStack looks as expected, I have on it only "Main" entry.
Also, when I add to backstack Fragment 2 I can back normally from Frag3 to Frag2 to Frag1 (but this is not what I want).
//Edit:
First:
I debug my app a little and I notice that when I press back button, Fragment is poped out from backstack and his lifecycle methods were invoked, but current fragment (Fragment 3) do nothing (I logged his onPause and onStop methods and they weren't invoked). Maybe this is a problem?
Second:
I found a solution that I implement onBackStackChange listener and in onBackStacChange method I simply replace Fragment3 with Fragment1. This works, but is it correct?
do it using....
FragmentManager fmManager = activity.getSupportFragmentManager();
if (fmManager.getBackStackEntryCount() > 0) { fmManager.popBackStack(fmManager.getBackStackEntryAt(fmManager.getBackStackEntryCount()-2).getId(), fmManager.POP_BACK_STACK_INCLUSIVE); }
-2 is because you want to go two 2 fragment step back
#Override
public void onPageScrollStateChanged(int state) {
int currentPage = mChannelPager.getCurrentItem();
if (currentPage == mChannelsList.size() - 1 || currentPage == 0) {
previousState = currentState;
currentState = state;
if (previousState == 1 && currentState == 0) {
mChannelPager.setCurrentItem((currentPage == 0 ? mChannelsList.size() - 1 : 0), false);
}
}
}
});
Write this code in your onPageChangeListner's onPageScrollStateChanged(int state)
1) Add First Fragment using below code
android.support.v4.app.FragmentManager fm = getActivity().getSupportFragmentManager();
android.support.v4.app.FragmentTransaction ft=fm.beginTransaction();
if (fm.findFragmentById(R.id.fragment_container) != null) {
ft.hide(fm.findFragmentById(R.id.fragment_container));
}
ft.add(R.id.fragment_container, new OneFragment(),OneFragment.class.getCanonicalName())
.addToBackStack(OneFragment.class.getCanonicalName()).commit();
2) Add Second Fragment From First fragment using below code
android.support.v4.app.FragmentManager fm = getActivity().getSupportFragmentManager();
android.support.v4.app.FragmentTransaction ft=fm.beginTransaction();
if (fm.findFragmentById(R.id.fragment_container) != null) {
ft.hide(fm.findFragmentById(R.id.fragment_container));
}
ft.add(R.id.fragment_container,new TwoFragment(),TwoFragment.class.getCanonicalName())
.addToBackStack(TwoFragment.class.getCanonicalName()).commit();
3) Add Third Fragment From Second fragment using below code
android.support.v4.app.FragmentManager fm = getActivity().getSupportFragmentManager();
android.support.v4.app.FragmentTransaction ft=fm.beginTransaction();
if (fm.findFragmentById(R.id.fragment_container) != null) {
ft.hide(fm.findFragmentById(R.id.fragment_container));
}
ft.add(R.id.fragment_container, new ThreeFragment(),ThreeFragment.class.getCanonicalName())
.addToBackStack(ThreeFragment.class.getCanonicalName()).commit();
4) onBackPressed() please write below code
#Override
public void onBackPressed() {
hideKeyboard(MainActivity.this);
Fragment currentFragment = this.getSupportFragmentManager().findFragmentById(R.id.fragment_container);
if (currentFragment.getClass().getName().equalsIgnoreCase(ThreeFragment.class.getName())) { // Using this code come from third fragment to first fragment
Fragment f = this.getSupportFragmentManager().findFragmentByTag(TwoFragment.class.getCanonicalName());
if (f != null) {
this.getSupportFragmentManager().popBackStackImmediate(f.getClass().getCanonicalName(), FragmentManager.POP_BACK_STACK_INCLUSIVE);
}
}else {
super.onBackPressed();
}
}
My activity is composed of 3 nested Fragments. There is my MainFragment that is displayed by default, ProductFragment that can be called from it, then DetailFragment can be called from ProductFragment.
I can go back and forth between my ProductFragment and DetailFragment. By doing so, the popStackBack method is accumulating similar fragments. Then, if I click on the back button, It will go back through all the Fragments as many time I called them.
What is the proper way to avoid the same Fragment to be kept in the back stack ?
EDIT :
I firstly call my main fragment :
if (savedInstanceState == null) {
getFragmentManager()
.beginTransaction()
.add(R.id.container, new SearchFragment(), "SEARCH_TAG")
.commit();
}
Here is the code that calls the fragments from the activity :
FragmentManager fm = getFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.setCustomAnimations(R.animator.enter_from_bottom, R.animator.exit_to_top, R.animator.enter_from_bottom, R.animator.exit_to_top);
ft.replace(R.id.container, new FactFragment(), "FACT_TAG");
ft.addToBackStack("FACT_TAG");
ft.commit();
Then, on back click :
#Override
public void onBackPressed() {
getFragmentManager().popBackStack();
}
I tried to get the tag of my current fragment and execute some specific code related to it but it doesn't work well. I also tried to addToBackStack() only when current Fragment wasn't already added to the backStack but it messed up my fragment view.
Use fragment's method isAdded() to evaluate the insertion. For example:
if(!frag.isAdded()){
//do fragment transaction and add frag
}
Here is my solution. Maybe dirty but it works. I implemented a method that returns the tag of the fragment that is displayed before clicking the on back button :
public String getActiveFragment() {
if (getFragmentManager().getBackStackEntryCount() == 0) {
return null;
}
String tag = getFragmentManager()
.getBackStackEntryAt(getFragmentManager()
.getBackStackEntryCount() - 1)
.getName();
return tag;
}
Then, on my onBackPressed() method :
// Get current Fragment tag
String currentFrag = getActiveFragment();
if(currentFrag.equals("PRODUCT_TAG")) {
// New transaction to first Fragment
FragmentManager fm = getFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.setCustomAnimations(R.animator.enter_from_right, R.animator.exit_to_left, R.animator.enter_from_right, R.animator.exit_to_left);
ft.replace(R.id.container, new SearchFragment(), "MAIN_TAG");
ft.commit();
} else {
// Go to Fragment-1
getFragmentManager().popBackStack();
}
Here is my handy and simple solution to check for duplicate insertion through fragment manager
at first, I check if it is first time intention for adding fragment and then I check if the fragment is presented using fragment manager
Fragment fragment = getSupportFragmentManager().findFragmentByTag("firstFragment");
if (fragment == null) {
getSupportFragmentManager().beginTransaction().add(R.id.frameLayout, new FirstFragment(), "firstFragment")
.addToBackStack(null)
.commit();
}else if(!fragment.isAdded()){
getSupportFragmentManager().beginTransaction().add(R.id.frameLayout, new FirstFragment(), "firstFragment")
.addToBackStack(null)
.commit();
}
Here is my solution:
Fragment curFragment = fragmentManager.findFragmentById(R.id.frameLayout);
if(curFragment != null
&& curFragment.getClass().equals(fragment.getClass())) return;
// add the fragment to BackStack here
Xamarin.Android (C#) version:
var curFragment = fragmentManager.FindFragmentById(Resource.Id.frameLayout);
if (curFragment != null
&& curFragment.GetType().Name == fragment.GetType().Name) return;
// add the fragment to BackStack here
I'm working on an android application, that uses a navigation drawer to switch between two fragments. However, each time I switch, the fragment is completely recreated.
Here is the code from my main activity.
/* The click listener for ListView in the navigation drawer */
private class DrawerItemClickListener implements ListView.OnItemClickListener {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
selectItem(position);
}
}
private void selectItem(int position) {
android.support.v4.app.Fragment fragment;
String tag;
android.support.v4.app.FragmentManager; fragmentManager = getSupportFragmentManager();
switch(position) {
case 0:
if(fragmentManager.findFragmentByTag("one") != null) {
fragment = fragmentManager.findFragmentByTag("one");
} else {
fragment = new OneFragment();
}
tag = "one";
break;
case 1:
if(fragmentManager.findFragmentByTag("two") != null) {
fragment = fragmentManager.findFragmentByTag("two");
} else {
fragment = new TwoFragment();
}
tag = "two";
break;
}
fragment.setRetainInstance(true);
fragmentManager.beginTransaction().replace(R.id.container, fragment, tag).commit();
// update selected item and title, then close the drawer
mDrawerList.setItemChecked(position, true);
setTitle(mNavTitles[position]);
mDrawerLayout.closeDrawer(mDrawerList);
}
I've set up some debug logging, and every time selectItem is called, one fragment is destroyed, while the other is created.
Is there any way to prevent the fragments from being recreated, and just reuse them instead?
After #meredrica pointed out that replace() destroys the fragments, I went back through the FragmentManager documentation. This is the solution I've come up with, that seems to be working.
/* The click listener for ListView in the navigation drawer */
private class DrawerItemClickListener implements ListView.OnItemClickListener {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
selectItem(position);
}
}
private void selectItem(int position) {
android.support.v4.app.FragmentManager; fragmentManager = getSupportFragmentManager();
switch(position) {
case 0:
if(fragmentManager.findFragmentByTag("one") != null) {
//if the fragment exists, show it.
fragmentManager.beginTransaction().show(fragmentManager.findFragmentByTag("one")).commit();
} else {
//if the fragment does not exist, add it to fragment manager.
fragmentManager.beginTransaction().add(R.id.container, new OneFragment(), "one").commit();
}
if(fragmentManager.findFragmentByTag("two") != null){
//if the other fragment is visible, hide it.
fragmentManager.beginTransaction().hide(fragmentManager.findFragmentByTag("two")).commit();
}
break;
case 1:
if(fragmentManager.findFragmentByTag("two") != null) {
//if the fragment exists, show it.
fragmentManager.beginTransaction().show(fragmentManager.findFragmentByTag("two")).commit();
} else {
//if the fragment does not exist, add it to fragment manager.
fragmentManager.beginTransaction().add(R.id.container, new TwoFragment(), "two").commit();
}
if(fragmentManager.findFragmentByTag("one") != null){
//if the other fragment is visible, hide it.
fragmentManager.beginTransaction().hide(fragmentManager.findFragmentByTag("one")).commit();
}
break;
}
// update selected item and title, then close the drawer
mDrawerList.setItemChecked(position, true);
setTitle(mNavTitles[position]);
mDrawerLayout.closeDrawer(mDrawerList);
}
I also added this bit, but I'm not sure if it's necessary or not.
#Override
public void onDestroy() {
super.onDestroy();
FragmentManager fragmentManager = getSupportFragmentManager();
if(fragmentManager.findFragmentByTag("one") != null){
fragmentManager.beginTransaction().remove(fragmentManager.findFragmentByTag("one")).commit();
}
if(fragmentManager.findFragmentByTag("two") != null){
fragmentManager.beginTransaction().remove(fragmentManager.findFragmentByTag("two")).commit();
}
}
Use the attach/detach method with tags:
Detach will destroy the view hirachy but keeps the state, like if on the backstack; this will let the "not-visible" fragment have a smaller memory footprint. But mind you that you need to correctly implement the fragment lifecycle (which you should do in the first place)
Detach the given fragment from the UI. This is the same state as when it is put on the back stack: the fragment is removed from the UI, however its state is still being actively managed by the fragment manager. When going into this state its view hierarchy is destroyed.
The first time you add the fragment
FragmentTransaction t = getSupportFragmentManager().beginTransaction();
t.add(android.R.id.content, new MyFragment(),MyFragment.class.getSimpleName());
t.commit();
then you detach it
FragmentTransaction t = getSupportFragmentManager().beginTransaction();
t.detach(MyFragment.class.getSimpleName());
t.commit();
and attach it again if switched back, state will be kept
FragmentTransaction t = getSupportFragmentManager().beginTransaction();
t.attach(getSupportFragmentManager().findFragmentByTag(MyFragment.class.getSimpleName()));
t.commit();
But you always have to check if the fragment was added yet, if not then add it, else just attach it:
if (getSupportFragmentManager().findFragmentByTag(MyFragment.class.getSimpleName()) == null) {
FragmentTransaction t = getSupportFragmentManager().beginTransaction();
t.add(android.R.id.content, new MyFragment(), MyFragment.class.getSimpleName());
t.commit();
} else {
FragmentTransaction t = getSupportFragmentManager().beginTransaction();
t.attach(getSupportFragmentManager().findFragmentByTag(MyFragment.class.getSimpleName()));
t.commit();
}
The replace method destroys your fragments. One workaround is to set them to Visibility.GONE, another (less easy) method is to hold them in a variable. If you do that, make sure you don't leak memory left and right.
I did this before like this:
if (mPrevFrag != fragment) {
// Change
FragmentTransaction ft = fragmentManager.beginTransaction();
if (mPrevFrag != null){
ft.hide(mPrevFrag);
}
ft.show(fragment);
ft.commit();
mPrevFrag = fragment;
}
(you will need to track your pervious fragment in this solution)
I guess you can not directly manipulate the lifecycle mechanisms of your Fragments. The very fact that you can findFragmentByTag is not very bad. It means that the Fragment object is not recreated fully, if it is already commited. The existing Fragment just passes all the lifecycle steps each Fragment has - that means that only UI is "recreated".
It is a very convenient and useful memory management strategy - and appropriate, in most cases. Fragment which is gone, has the resources which have to be utilized in order to de-allocate memory.
If you just cease using this strategy, the memory usage of your application could increase badly.
Nonetheless, there are retained fragments, which lifecycle is a bit different and do not correspond to the Activity they are attached to. Typically, they are used to retain some things you want to save, for example, to manage configuration changes
However, the fragment [re]creation strategy depends on the context - that is, what you would like to solve, and what are the trade-offs that you are willing to accept.
Just find the current fragment calling getFragmentById("id of your container") and then hide it and show needed fragment.
private void openFragment(Fragment fragment, String tag) {
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
Fragment existingFragment = fragmentManager.findFragmentByTag(tag);
if (existingFragment != null) {
Fragment currentFragment = fragmentManager.findFragmentById(R.id.container);
fragmentTransaction.hide(currentFragment);
fragmentTransaction.show(existingFragment);
}
else {
fragmentTransaction.add(R.id.container, fragment, tag);
}
fragmentTransaction.commit();
}
Same idea as Tester101 but this is what I ended up using.
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
Fragment oldFragment = fragmentManager.findFragmentByTag( "" + m_lastDrawerSelectPosition );
if ( oldFragment != null )
fragmentTransaction.hide( oldFragment );
Fragment newFragment = fragmentManager.findFragmentByTag( "" + position );
if ( newFragment == null )
{
newFragment = getFragment( position );
fragmentTransaction.add( R.id.home_content_frame, newFragment, "" + position );
}
fragmentTransaction.show( newFragment );
fragmentTransaction.commit();
Hide easily in kotlin using extensions:
fun FragmentManager.present(newFragment: Fragment, lastFragment: Fragment? = null, containerId: Int) {
if (lastFragment == newFragment) return
val transaction = beginTransaction()
if (lastFragment != null && findFragmentByTag(lastFragment.getTagg()) != null) {
transaction.hide(lastFragment)
}
val existingFragment = findFragmentByTag(newFragment.getTagg())
if (existingFragment != null) {
transaction.show(existingFragment).commit()
} else {
transaction.add(containerId, newFragment, newFragment.getTagg()).commit()
}
}
fun Fragment.getTagg(): String = this::class.java.simpleName
Usage
supportFragmentManager.present(fragment, lastFragment, R.id.fragmentPlaceHolder)
lastFragment = fragment
Here's what I'm using for a simple 2 fragment case in Kotlin:
private val advancedHome = HomeAdvancedFragment()
private val basicHome = HomeBasicFragment()
override fun onCreate(savedInstanceState: Bundle?) {
...
// Attach both fragments and hide one so we can swap out easily later
supportFragmentManager.commit {
setReorderingAllowed(true)
add(R.id.fragment_container_view, basicHome)
add(R.id.fragment_container_view, advancedHome)
hide(basicHome)
}
binding.displayModeToggle.onStateChanged {
when (it) {
0 -> swapFragments(advancedHome, basicHome)
1 -> swapFragments(basicHome, advancedHome)
}
}
...
}
With this FragmentActivity extension:
fun FragmentActivity.swapFragments(show: Fragment, hide: Fragment) {
supportFragmentManager.commit {
show(show)
hide(hide)
}
}
How about playing with the Visible attribute?
this is a little late response.
if you're using view pager for fragments, set the off screen page limit of the fragment to the number of fragments created.
mViewPager.setOffscreenPageLimit(3); // number of fragments here is 3